Voltage breakdown test circuit



Feb.'16, 1965 c. J. TABoR, JR 3,170,115

VOLTAG BREAKDOWN TEST CIRCUIT Filed July 20, 1960 2 Sheets-Sheet lUnited States Patent() 3,170,115 vormen nanAKnowN rnsr crncrnr Clarence.1. Tabor, 1r., Schneclrsviiie, Pa., assigner to Western ElectricCompany, Incorporated, New York, NX., a corporation of New York Filed.luiy 20, 1969, Ser. No. 44,053 v 5 Claims. (Cl. 324-51) This inventionrelatestoV devices for determining electrical characteristics betweenconductors and particularly to devices for testing leakage betweennormallyginsulatedV conductive elements and` conductivity betweenelements normally joined by a conductive path.

i The necessity in electrical devices of restricting current l flow tothe conductive paths designed to accommodate such'tiow andot minimizingcurrent ow elsewhere is obvious and basic. Consequently, currentcontinuity and leakage testsL areof 'principal importancein.determiningthe adequacy of circuitry or components for their intended purpose.Tests of this type are usually simple and tested against every otherpoint,`the establishment of the multiple, successive contacts is'quitetime consuming Vand costly. In large scale production there is anincreasing.

tendency for 100 percent -testing ofthe product to insure reliability,and the undesirable high te'st costs urge particularly toward reductionof test time. Examples ofsuch 1 products are electron tubes and relaysin both`ofwhich interelectrode or intercontact leakage must( be strictlycontrolled. The problem can be appreciated by considering that it iscommon. for relays to have as many asnine independent elements. Hence,in order to test each ele' ment with every other element, a series ofthirty-six separate tests must be made.

Itfis, therefore, an objectof the invention to reduce continuity andleakage testing time when a plurality of elements must be tested inpairs.

Another object of the invention is to provide a device which cansimultaneously test between several of the points to be tested Vforeither leakage or continuity and after a simple switching actionsimultaneously complete the remaining tests' so that every point hasbeen tested with every other point in only two steps.

The invention is-embodied in testing devices for'determining electricalleakage or continuity between pairs of a plurality of elements. A sourceof polyphase voltage is connectedV so that approximately equal numbersof different elements are connected to each phase. Detectors areconnected to each element for indicating an excess of leakage currentbetween elements in the leakage test device or a deficiency of currentin the continuity test device.

ln accordance with one feature of the invention, switching is providedto transfer elements which shared the same phase to different phases sothat in two steps every element is tested against everyother element.

In one specific embodiment of the invention particularly useful forthe'leakage testing ofrelays in whichY certain elements are shortedtogether vby a contact arm,

FIG. 2 is a schemat-ic of a relay leakage tester according to theinvention.

Referring now to the drawing, FIG. 1 represents a general embodiment ofthe invention appropriate for either a continuity or leakagetest whennine or fewer ,elements shown generallyas 11-19 are to be individuallychecked with every other element. The combination of nine elements takentwoat a time requires thirty-six separate tests. i

`Reduction. of thetirne involved in makingV thirty-six independenttestsis realized by the application of two features. First, a three-phase.(gbA, qbB, 95C) source 20 of alternating current test voltage is used.This -permits three elements to be connected to each phase: bA-11, 14,`17; PB-12, 15, 18; qC-13, 16, 19. Each element can be tested againsteach of the elements connected to the other phases simultaneously.Second, since each phase is con- Y nected to moreV than one element,several groups of contacts are being tested at the same time. Thus, eacheleinent on A will be tested against all three elements on 15B and allthree elements on C, and eighteen tests can be made at one time., y p

The remaining eighteen tests involving those elements which shared acommon phase'during the rst eighteen tests areaccomplished by-switchingthe phase-element connections to new combinations by means of ganged Yswitch 30 which throws the contact arms 271-29, associated with elements11-19,j respectively, to their lower position. The new combination ofelements and phases is then as follows: A-11, 12, 13;'SB-14, 15, 16;C-17, 13, 19'. All of the pairs not tested in the 'rst combination aretested simultaneously after the switching action of combinationlaltering switch 30. All of the thirty-six tests required have beenaccomplished with one switching action. and two Vtest periods, savingthe time that would have been expended on thirty-four tests. V Detectioncircuits 31-39 are connected to each one of the elements 11-19.`Detectors 31-39 will, of coursefoe different Vfor the leakage and the'continuity tests. The detector 5150i FIG. 2 shows a convenient andsimple form of detector for the leakage Vtest and will be described morecompletely in connection with the embodiment of FIG. 2. The leakagedetector is essentially senistive to high current while an appropriatecontinuity testerwould be sensitive to low current values. Any one ofthe large number of current sensitive devices known in the art may beused.` Y

FIG. 2 represents schematically one embodiment of the invention usedforchecking breakdown or leakage between elements (e1-69) of a mercuryrelay 60. For purposes of illustration, the standards to which relay 60is subjected are taken from the standards from an actual the deviceincludes means for applying power to transfer the arm and isolate thepreviously shorted elements. The now isolated elements are connected tothe different input phrases so that leakage tests can be made betweenthem. The invention will be described in connection with the 'drawing inwhich: y j FIG. 1` isga schematic 'of the general embodiment of theinvention utilizing la three-phase test voltage; and

relay. The breakdown test inthis case is achieved by applying1,000'volts across each of the two relay elements throughsuitable'dropping resistors analogous to resistor 71 in detectorSl.Potentiometer 72 maybe adjusted so that the indicator lamp 73 willV glowwhen a given resistance is inserted between any vtwo detector circuitsbut will not glow when a larger resistance is connected in :the samephase.

Elements that are electrically connected either by sharing the samephase or Vby being shorted to a common point cannot be leakage checkedone against the other. The arrangement of'contacts in relay 60 thusprecludes the testing `of elements 63, 64 and 65 against veach otherwhen the relay is de-energized. Consequently, these elements are placedin` the same phasefwhen the relay is rie-energized 'and ,in differentphases lwhen the relay is energized. Conversely, elements 61, 62 and 63are incapable of being checked against each other when the `relay isenergized, but are capable of being checked one against the other whenthe relay is deenergized. Thus, these elements are connected indifferent phases when the relay is ele-energized and in the same phasewhen the relay is energized.

Technically, it is not possible to check the elements 66, 68 and 69 ofthe relay coil 76 against each other for leakage, since an ohmic pathdoes exist between those points. However, it is possible by applyingtest voltage to those points and by adjusting the associated detectorsto check the integrity of the coil, that is, to check that no leakageexists between the coil windings. If any leakage exists between the coilwindings the resistance of the coil 76 will be less than the speciiiedvalue and the detectors associatedwith that .portion of the coil '76wherein the leakage exists will light.

Power supplied by DC. power source 77 applies actuating voltage to thecoil 76 through switch contacts 74 and 75 when switch 50 has moved 74and 75 to their lower position. This application of ypower to the coilpulls t .e contact arm 78,associated with element 63 to its lowerposition while switch contacts 42, 43 and i4 simultaneously placeelements 63, 64 and 65, respectively, in different phases. At the sametime switch contacts 44, 45 and 45 place the elements'l, 62 and 65 in42A. Actuation of the combination altering switch 50 places the contactsl1-,49 in their lowerl position. This functions to place-those elementsin a different position which shared a common phase with the switchcontacts Ail-49l in their upper position. In this way, all the elementsare checked against all other elements in only two tests. Since eachelement has its own indicator 73, no disadvantage resultsL from havingelements connected to each phase as the test will shown breakdownbetween an element in one phase and any element in the other two phasesby lighting the two indicator lamps, one in each ofthe two phases,between which the breakdown occurs.

It is to be understood that the above described arrangements are simplyillustrative of the principles of the invention. Other arrangementsv maybe readily devised by those skilled in the art, to accommodate theinvention Vto numerous practical situations, which will embody theprinciples of the invention and fall within its spirit and scope.

What is claimed is:

l. yApparatus for testing a plurality of elements to determine whetherthere is any leakage therebetween, which comprises:

a source of polyphase voltage having a plurality of output leadscorresponding to the direrent phases thereof;

switching means selectively operable from a first to a second positionfor connecting said elements to the output leads of said polyphasevoltage source, in said first position a plurality of first groups ofthe elements being connected to said output leads in 'a manner such thateach of said first groups is connected to a different output lead, andin said second position a plurality of second groups of the elementsbeing connected to said output leads in a manner such that each .of saidsecond groups is connected to a different output lead, said first andsecond groups being selected such that those elements belonging to thesame first group are each in a different second group;

means connected to each element and responsive to a predeterminedcurrent therethrough for indicating leakage between that element and anyof the other elements; and

means for operating said switching means fromY its first to its secondposition whereby each of said elements is tested for leakage to any ofthe other of said elements.

'2.- Apparatus for testing a plurality7 of elements to determine whetherthere is any leakage therebetween, which comprises:

a three phase voltage source having three output leads,

v one for each of said three phases;

a plurality of current indicating detectors having rst and second inputterminals, each detector first input terminal being connected to one ofthe elements;

switching means selectively operable from a first to a second positionfor connecting said detectors to the output leads of said polyphasevoltage source, in said iirst position a pluralityof first groups of thedetectors being connected to said output leads in a manner such thateach of said first groups is connected to a different output lead and insaid second position a plurality of second groups of the vdetectorsbeing connected to said output leads in a manner such that each of saidsecond groups is connected to a different output lead, said first andsecond groups being selected such that those detectors belonging to thesame first group are each in a different second group; and

means for operating said switching means from its first to its secondposition whereby each of said elements is tested for leakage to any ofthe other of said y elements.

3. Apparatus for testing a plurality of elements to determine whetherthere is any leakage therebetween, some of said elements being normallyin electrical contact with one another and the other of said elementsbeing electrically isolated from one another, which apparatuscornprises:

a polyphase source of electrical voltage having a plurality of outputleads, atleast one for each phase;

switching means selectively operable from a first to a second positionfor connecting groups of said elements to different output leads' ofsaid polyphase voltage source with one group being connected to eachoutput lead, in said first position these elements normally inelectrical contact being members of the same group and in said secondposition those elements which were members of the same group in saidfirst-position being members of a different group;

means connected to each element and responsive to a predeterminedcurrent therethrough for indicating leakage between that element and anyof the other elements;

means for electrically isolating from each other those elements whichare normally in electrical contact with one ano-ther; and y means foroperating said switching means from its first to its second positionwhereby each of said elements is tested for leakage to any of the otherelements.

4. lApparatus for testing a plurality of elements to determine whetherthere is any leakage therebetween, some of said elements being normallyin electrical contact with one another and the other of said elementsbeing electrically isolated from one another, which apparatus comprises:

a three phase voltage source having three output leads,

one for each of said three phases; l

a plurality of current indicating detectors having first and secondinput terminals, each detector first input terminal being connected toone of the'elements;

switching means operable from a first to a second position forconnecting the second input terminals of said detectors to the threeoutput leads of said three phase voltage source with approximatelyone-third of the detectors being connected to each output lead, in saidiirst position the detectors connected to those elements normally inelectrical contact with each other being connected to vthe same outputlead and in said second position those detectors connected to the sameoutput lead in said first posi- -tion being connected to differentoutput leads;

Y means for electrically isolating from each other those elements whichare normally in electrical contact with one another; and means for`operating said switching means from its rst to its second positionwhereby each of said elements References Cited in the le of this patentUNITED STATESl PATENTS 1,918,834 Crago July 18, 1933 2,094,645 t FoulkeOct. S, 1937 2,509,815 Elliot May 30, 1950 2,593,225 Van Ryan et al.Apr. 15, 1952 2,610,229 Cranford Sept. 9, 1952 2,805,391 Meadows et al.Sept. 3, 1957 2,806,185' Oberman Sept. 10, 1957 Y FOREIGN PATENTS737,746 Great Britain Sept. 28, 1955 OTHER REFERENCES

1. APPARATUS FOR TESTING A PLURALITY OF ELEMENTS TO DETERMINE WHETHERTHERE IS ANY LEAKAGE THEREBETWEEN, WHICH COMPRISES: A SOURCE OFPOLYPHASE VOLTAGE HAVING A PLURALITY OF OUTPUT LEADS CORRESPONDING TOTHE DIFFERENT PHASES THEREOF; SWITCHING MEANS SELECTIVELY OPERABLE FROMA FIRST TO A SECOND POSITION FOR CONNECTING SAID ELEMENTS TO THE OUTPUTLEADS OF SAID POLYPHASE VOLTAGE SOURCE, IN SAID FIRST POSITION APLURALITY OF FIRST GROUPS OF THE ELEMENTS BEING CONNECTED TO SAID OUTPUTLEADS IN A MANNER SUCH THAT EACH OF SAID FIRST GROUPS IS CONNECTED TO ADIFFERENT OUTPUT LEAD, AND IN SAID SECOND POSITION A PLURALITY OF SECONDGROUPS OF THE ELEMENTS BEING CONNECTED TO SAID OUTPUT LEADS IN A MANNERSUCH THAT EACH OF SAID SECOND GROUPS IS CONNECTED TO A DIFFERENT OUTPUTLEAD, SAID FIRST AND SECOND GROUPS BEING SELECTED SUCH THAT THOSEELEMENTS BELONGING TO THE SAME FIRST GROUP ARE EACH IN A DIFFERENTSECOND GROUP; MEANS CONNECTED TO EACH ELEMENT AND RESPONSIVE TO APREDETERMINED CURRENT THERETHROUGH FOR INDICATING LEAKAGE BETWEEN THATELEMENT AND ANY OF THE OTHER ELEMENTS; AND